Flash lamp



April 3, 1956 w, HONlNG ETAL FLASH LAMP Filed Oct. 19, 1951 5 0 63 msec.

aux/d IN V EN TORS WILHELM NONiNG .HHOH WIJNBERG States Pate FLASH LAMPWilhelm Honing and Simon Wijnberg, Eindhoven, Netherlands, assignors toHartford National Bank and Trust Company, Hartford, Conn., 'as trusteeApplication October 19, 1951, Serial No. 252:,054 Claims. (Cl. 67-31)This invention relates to electrically ignited flash lamps comprising abulb which contains a solid material in the form of foils, strips orwires burning actinically together with oxygen which produces anemission of light. The bulb also contains an oxygen containing gasmixture. The invention more particularly relates to small sized flashlamps having a bulb volume of 35 ccs. or less, which permit a very shortflash to be obtained. Such flash lamps are widely used in takingphotographic pictures when the natural illumination is insuflicient.

It has been proposed to speed up the combustion of the actinicallyburning material by mixing the oxygen gas with a combustible auxiliarygas in the bulb of a flash lamp. Since, however, the combustion of theauxiliary gas takes in an explosive manner, its content must not beraised excessively if bursting of the bulb is to be avoided uponignition.

In carrying the invention through it has been found that with the use ofa mixture of acetylene and oxygen, the defiegration is not too vigorousso that a high acetylene percentage of approximately 7 to percent byvolume may be employed without unduly increasing the risk of bursting ofthe bulb.

The present invention concerns an electrically ignited flash lamp whosebulb, the volume of which is less than 35 ccs., contains a solidmaterial in the form of foils, tapes, wires burning actinically togetherwith oxygen with the emission of light and furthermore contains acombustible gas mixture, which gas mixtures contain acetylene.

The acetylene content to be used in the gas mixture depends upon thefineness of the dimensions of the actinically burning material and inaddition upon the rate at which the combustion is to take place. Thisrate of combustion is naturally also influenced by other structuralfeatures. Thus, for example, a flash lamp in which a short combustiontime is required, will preferably be given a spherical, egg-shaped oroval section. Furthermore, the ignition will preferably take placecentrally by means of an ignition paste, even if the gas mixture can beignited by means of a filament or a spark. As a matter of fact it hasbeen found that, even if the flash lamp contains a suificient quantityof acetylene gas to be ignited by a conducting wire or a spark, anignition paste permits the combustion to be speeded up somewhat. Theinvention is particularly suitable for use in flash lamps in which atime of combustion of 15 milliseconds or shorter is required as is thecase in some cameras.

In a great number of modern cameras a synchronizer is built, whichcauses the flash to coincide with the short period during which theshutter is open. For practical reasons such cameras require only flashlamps whose flash terminates within 15 milliseconds after switching onthe current. With the existing flash lamps of this type this period isusually much longer, for example 35 milliseconds.

The invention permits the manufacture of flash lamps having a time ofcombustion of 15 milliseconds or shorter ICC without the fineness of theproportions of the actinically burning material needing'to be raised toa degree exceeding that of flash lamps of known customary types.

Thus, for'example, the invention permits a flash lamp to be made whichfulfils this conditionwhile employing actinically burning materialconsisting of a filamentary aluminum-magnesium, alloy approximately 32/a thick.

For relative comparison of flash lamps, the time of combustion is readoff from the curve indicating the relationexisting between luminousintensity and time. The term time of combustion is to be understood tomean the time elapsing between operation of the ignition contact and theinstant at which the luminous intensity, after having reached a maximum,has dropped to 50% of its maximum value.

In order that the invention may be more clearly understood and readilycarried into efiect, it will now be described more fully with referenceto the accompanying drawing in which:

Figure 1 represents one embodiment of a bulb of the invention.

Figures 2 and 3 show time-luminous intensity curves for two bulbs.

The reference numeral 1 designates a glass bulb having a volume of 30ccs., a cap 2 to which an electric conductor 3 is secured. An electricconductor 4 is secured to terminal contact 5. The electric conductors 3and 4 are connected at 6 to a filament 7 which fires the ignition paste8 upon the passage of current. The reference numeral 9 designatescombustible material consisting of wires of an aluminum-magnesium alloycontaining 7% of magnesium. The wires are 32/;1. thick, their overallweight being 15 mgms. The gas-filling 10 consists of a mixture of oxygenand acetylene. In the drawing, one curve illustrates the relationexisting between luminous intensity and time. Fig. 2 shows thecombustion curve of the above described flash lamp whose gas-filling hasan acetylene content of volume percent. Fig. 3 showing the same curvefor a corresponding lamp whose gas-filling consists of oxygen containing8 volume percent of acetylene.

In the table below, the values of the time of combustion, derived fromthese curves, are expressed in milliseconds.

Acetylene content: Time of combustion What we claim is:

1. An electrically ignited flash lamp comprising a bulb of a radiationtransmitting material and having a volume of less than 35 ccs., anactinically active solid material within said bulb in the form of foilshaving a thickness of approximately 32/ ,u, a filling atmosphere withinsaid bulb including oxygen and a combustible gas mixture of acetylene insuch an amount to eifect a time of combustion of no more than 15milliseconds, and ignition means within said bulb to ignite saidmaterial which actinically burns in said oxygen to produce an emissionof light.

2. An electrically ignited flash lamp comprising a bulb of a radiationtransmitting material and having a volume of less than 35 ccs., anactinically active solid material in the form of strips, a fillingatmosphere within said bulb including oxygen and a combustible gasmixture of 7 to 15 percent acetylene by volume, and ignition meanswithin said bulb for igniting said material which actinically burns insaid oxygen to produce an emission of light.

3. An electrically ignited flash lamp comprising a bulb of radiationtransmitting material having at least two terminals therein, said bulbhaving a volume of less than 35 ccs., an actinically active solidmaterial within said bulb in the form of strips, a filling atmospherewithin said bulb 15 per cent acetylene by volume, a filament connectedtov said terminals, and ignition paste within said bulb and on saidfilament to ignite said material which actinically burns in said oxygento produce an emission of light.

4. An electrically ignited flash lamp comprising a bulb of radiationtransmitting material having a volume of less than 35 ccs., anactinically active solid aluminum-magnesium alloy in foil-like formwithin said bulb and having a thickness of approximately 32/ n, afilling atmosphere within said bulb including oxygen and a combustiblegas mixture of 7 to 15 per cent acetylene by volume, and ignition meanswithin said bulb to ignite said material which actinically burns in saidoxygen to produce an emission of light.

5. An electrically ignited flash lamp comprising a substantiallyoval-shaped bulb of radiation transmitting material and having a volumeof less than 35 cos, an actinically active solid material in foil-likeform within said bulb, a filling atmosphere within said bulb includingoxygen and a combustible gas mixture of 7 to 15 per cent acetylene byvolume, and ignition means located centrally in said bulb to ignite saidmaterial which actinically burns in said oxygen to produce an emissionof light.

References Cited in the file of this patent UNITED STATES PATENTSNichols Mar. 26, 1935 Lemmers Oct. 31, 1939

3. AN ELECTRICALLY IGNITED FLASH LAMP COMPRISING A BULB OF RADIATIONTRANSMITTING MATERIAL HAVING AT LEAST TWO TERMINALS THEREIN, SAID BULBHAVING A VOLUME OF LESS THAN 35 CCS., AN ACTINICALLY ACTIVE SOLIDMATERIAL WITHIN SAID BULB IN THE FORM OF STRIPS, A FILLING ATMOSPHEREWITHIN SAID BULB INCLUDING OXYGEN AND A COMBUSTIBLE GAS MIXTURE OF 7 TO15 PER CENT ACETYLENE BY VOLUME, A FILAMENT CONNECTED TO SAID TERMINALS,AND IGNITION PASTE WITHIN SAID BULB AND ON SAID FILAMENT TO IGNITE SAIDMATRIAL WHICH ACTINICALLY BURNS IN SAID OXYGEN TO PRODUCE AN EMISSION OFLIGHT.